I am so sorry that you had this in your face today, but as you said..the past couple of weeks he's been staying out all night, being mean, and an arrogant jerk. Saying HE shouldn't have come back to you.
Honey when these changes appear, you can almost smell the booze suckering them in to another round of drinks.
He is right when he says he shouldn't have come back to you, because he was not ready or strong enough, and may never be.
If you don't want this to keep on, it looks like it goes back to where you were before he begged to come back, and let him go elsewhere to muck up, while you re-arrange your life around you and your young son, without the pain and hassle of a drunken jerk around you.
I don't know whether you have kept up going to Alanon, if so get all the support you can til next meeting, if not, then I am sure you still have numbers of members to call on. It won't worry them if you have been gone a while, as all they hear is one of them in pain and needed a hand.
I will keep you in my thoughts and my prayers.
God bless